The Carpal Tunnel Syndrome—A Review of 100 Patients Treated Surgically

The carpal tunnel syndrome, or compression neuropathy of the median nerve at the wrist, is a common cause of burning pain, numbness and tingling in the hand. The diagnosis is suggested by nocturnal paresthesias in the thumb, index and long fingers associated with signs of irritability of the median nerve in the carpal tunnel at the wrist. Surgical treatment in the form of incision of the transverse carpal ligament should be performed before irreversible motor and sensory changes occur.     

Aneurysm of the median artery causing recurrent carpal tunnel syndrome and anatomic review

A patient is presented who had recurrent carpal tunnel syndrome symptoms in his left hand 1 year after having undergone release of the transverse carpal ligament. On exploration, this was found to be due to an aneurysm of a median artery and possibly scarring due to this compression around the branches of the bifurcated median nerve. This represents the first case in the literature to comment on (1) the absence of bilaterality of the anatomic finding and (2) carpal tunnel syndrome relative to median artery aneurysm. With this in mind, a plea is made for careful exploration of the carpal tunnel, maintaining an incision as far to the ulnar side of the median nerve as technically possible with thorough visualization of the contents of the tunnel and any anatomic variance involved. The incidence of the combination of aberrant median artery with high bifurcation of the median nerve is unknown, as is the incidence of aneurysm of the median artery.     

The effect of various adjuncts on the surgical treatment of carpal tunnel syndrome secondary to chronic tenosynovitis.

A series of 22 patients with carpal tunnel syndrome secondary to chronic tenosynovitis was divided into two groups. The first group was treated by transverse carpal ligament release alone. The second group was treated by transverse carpal ligament release, external neurolysis of the median nerve, flexor synovectomy, and intraoperative corticosteroid instillation. Both groups were comparable preoperatively as to symptoms, signs, and electrophysiological data. At two years postoperatively there were no statistically significant differences in the symptoms, signs, and electrophysiological data in the two groups. The only difference was that patients undergoing release alone were able to return to work earlier than those patients who had the adjunctive procedures.     

The incidence of recurrence after endoscopic carpal tunnel release

Endoscopic carpal tunnel release has been used to decompress the median nerve in carpal tunnel syndrome for over the past decade, with an advantage (over the traditional "open" release) being decreased pain in the postoperative period. The goals of this study were to attempt to define the recurrence rate after endoscopic carpal tunnel release and to determine if it differs from that of open technique. The charts of 191 consecutive carpal tunnel syndrome patients treated operatively at the University of Missouri were reviewed. For this study, recurrent carpal tunnel syndrome was defined as documented cases in which the symptoms had resolved following surgical release but subsequently recurred, requiring surgical rerelease of the carpal tunnel. All endoscopic releases were performed using the Chow two-portal technique. Statistical analysis was performed using Fisher's exact test. A total of 103 patient hands had open carpal tunnel releases; 88 were endoscopically released. Total follow-up time (from the initial release) averaged 29 months for the open group and 22 months for the endoscopic group. There were no recurrences in the open group and six recurrences in the endoscopic group (7 percent, p = 0.008). All six recurrences were in worker's compensation patients. The median time between endoscopic release and rerelease was 8.5 months. There seems to be a statistically higher incidence of recurrence of carpal tunnel syndrome after endoscopic release compared with the traditional "open" release in our cases. Although the pathogenesis of this increased rate of recurrence is not clear, this should be considered when planning surgical release of the volar carpal ligament for carpal tunnel syndrome.     

Carpal tunnel syndrome caused by hand injuries.

Although carpal tunnel syndrome associated with injury to the wrist is common, it is possible to overlook symptoms of median nerve compression caused by an ascending tenosynovitis secondary to trauma distal to the wrist. One should look for these symptoms in such patients who complain of pain and weakness of the hand, and release the carpal tunnel if nerve compression is suspected.     

A comparison of flexor tenosynovectomy, open carpal tunnel release, and open carpal tunnel release with flexor tenosynovectomy in the treatment of carpal tunnel syndrome

The purpose of this study was to identify the advantages and disadvantages of performing a flexor tenosynovectomy without dividing the transverse carpal ligament, an open carpal tunnel release, and an open carpal tunnel release with flexor tenosynovectomy in the treatment of carpal tunnel syndrome. From 1990 to 1998, a retrospective study was done in which a flexor tenosynovectomy was performed in 133 patients without division of the transverse carpal ligament and compared with 68 patients who had an open carpal tunnel release and 75 patients who had an open carpal tunnel release and flexor tenosynovectomy. Patients were followed up for an average period of 30 weeks with history and physical findings and nerve conduction velocities and for an average period of 2.6 years with telephone interviews. There was a 2.3 percent incidence of pillar pain in the flexor tenosynovectomy group, which may explain the earlier return to their regular jobs at an average time of 9.9 weeks, compared with 10.7 weeks for the carpal tunnel release group and 12.0 weeks for the carpal tunnel release/flexor tenosynovectomy group. The latter two groups had an incidence of pillar pain of 12.1 percent and 25.3 percent, respectively. Postoperative grip strength was statistically significantly improved in the flexor tenosynovectomy group compared with the other two groups, where adjustments were made for sex and preoperative grip strengths with standard error of adjusted means. In the flexor tenosynovectomy group, 20.6 percent of patients had a previous open or endoscopic carpal tunnel release with recurrent carpal tunnel syndrome, compared with 5.2 percent in the open carpal tunnel release group and 21.6 percent in the open carpal tunnel release with flexor tenosynovectomy group. Excisional biopsies of flexor tenosynovium in the flexor tenosynovectomy, open carpal tunnel release, and open carpal tunnel release with flexor tenosynovectomy groups revealed an incidence of fibrosis in 89.2 percent, 88.9 percent, and 87.7 percent of specimens, respectively. Edema was a frequent finding, but an active inflammatory response was seldom seen. The findings in this study indicate that because of a significant decrease in pillar pain, a flexor tenosynovectomy in the treatment of carpal tunnel syndrome would likely benefit workers who use the palm of the hand in heavy manual or highly repetitive work by allowing them to return to regular duty sooner.     

Volar/dorsal compressive mechanical behavior of the transverse carpal ligament

Mechanical insult to the median nerve caused by contact with the digital flexor tendons and/or carpal tunnel boundaries may contribute to the development of carpal tunnel syndrome. Since the transverse carpal ligament (TCL) comprises the volar boundary of the carpal tunnel, its mechanics in part govern the potential insult to the median nerve. Using unconfined compression testing in combination with a finite element-based optimization process, nominal stiffness measurements and first-order Ogden hyperelastic material coefficients (μ and α ) were determined to describe the volar/dorsal compressive behavior of the TCL. Five different locations on the TCL were tested, three of which were deep to the origins of the thenar and hypothenar muscles. The average (± standard deviation) low-strain and high-strain TCL stiffness values in compression sites outside the muscle attachment region were 3.6 N/mm (±2.7) and 28.0 N/mm (±20.2), respectively. The average stiffness values at compression sites with muscle attachments were notably lower, with low-strain and high-strain stiffness values of 1.2 N/mm (±0.5) and 9.7 N/mm (±4.8), respectively. The average Ogden coefficients for the muscle attachment region were 51.6 kPa (±16.5) for μ and 16.5 (±2.0) for α, while coefficients for the non-muscle attachment region were 117.8 kPa (±86.8) for μ and 17.2 (±1.6) for α. These TCL compressive mechanical properties can help inprove computational models, which can be used to provide insight into the mechanisms of median nerve injury leading to the onset of carpal tunnel syndrome symptoms.     

Finite element analysis for transverse carpal ligament tensile strain and carpal arch area

Mechanics of carpal tunnel soft tissue, such as fat, muscle and transverse carpal ligament (TCL), around the median nerve may render the median nerve vulnerable to compression neuropathy. The purpose of this study was to understand the roles of carpal tunnel soft tissue mechanical properties and intratunnel pressure on the TCL tensile strain and carpal arch area (CAA) using finite element analysis (FEA). Manual segmentation of the thenar muscles, skin, fat, TCL, hamate bone, and trapezium bone in the transverse plane at distal carpal tunnel were obtained from B-mode ultrasound images of one cadaveric hand. Sensitivity analyses were conducted to examine the dependence of TCL tensile strain and CAA on TCL elastic modulus (0.125–10 MPa volar-dorsally; 1.375–110 MPa transversely), skin-fat and thenar muscle initial shear modulus (1.6–160 kPa for skin-fat; 0.425–42.5 kPa for muscle), and intratunnel pressure (60–480 mmHg). Predictions of TCL tensile strain under different intratunnel pressures were validated with the experimental data obtained on the same cadaveric hand. Results showed that skin, fat and muscles had little effect on the TCL tensile strain and CAA changes. However, TCL tensile strain and CAA increased with decreased elastic modulus of TCL and increased intratunnel pressure. The TCL tensile strain and CAA increased linearly with increased pressure while increased exponentially with decreased elastic modulus of TCL. Softening the TCL by decreasing the elastic modulus may be an alternative clinical approach to carpal tunnel expansion to accommodate elevated intratunnel pressure and alleviate median nerve compression neuropathy.     

Median nerve compression and trigger finger in the mucopolysaccharidoses and related diseases.

Patients with Hurler's syndrome (MPS-1H), I-cell disease (ML-II) and pseudo-Hurler's syndrome (ML-III) had median nerve compression and triggering of the fingers which limited finger extension. To our knowledge, this combination has not been reported previously in patients with mucopolysaccharidoses and related disorders. In all of our 3 cases the median nerve was compressed by thickened flexor tenosynovium. Synovectomy and resection of the volar carpal ligament improved the hand function in all, including the mentally retarded patient with Hurler's syndrome. Release of the fibroosseous tunnel in two patients was followed by an increased range of motion (but not full extension). A fourth patient, without a mucopolysaccharide storage disorder, also had the combination of trigger finger and carpal tunnel syndrome.     

In Vivo Study of Transverse Carpal Ligament Stiffness Using Acoustic Radiation Force Impulse (ARFI) Imaging

The transverse carpal ligament (TCL) forms the volar boundary of the carpal tunnel and may provide mechanical constraint to the median nerve, leading to carpal tunnel syndrome. Therefore, the mechanical properties of the TCL are essential to better understand the etiology of carpal tunnel syndrome. The purpose of this study was to investigate the in vivo TCL stiffness using acoustic radiation force impulse (ARFI) imaging. The shear wave velocity (SWV) of the TCL was measured using Virtual Touch IQ^TM software in 15 healthy, male subjects. The skin and the thenar muscles were also examined as reference tissues. In addition, the effects of measurement location and ultrasound transducer compression on the SWV were studied. The SWV of the TCL was dependent on the tissue location, with greater SWV values within the muscle-attached region than those outside of the muscle-attached region. The SWV of the TCL was significantly smaller without compression (5.21 ± 1.08 m/s) than with compression (6.62 ± 1.18 m/s). The SWV measurements of the skin and the thenar muscles were also affected by transducer compression, but to different extents than the SWV of the TCL. Therefore to standardize the ARFI imaging procedure, it is recommended that a layer of ultrasound gel be maintained to minimize the effects of tissue compression. This study demonstrated the feasibility of ARFI imaging for assessing the stiffness characteristics of the TCL in vivo, which has the potential to identify pathomechanical changes of the tissue.     

Comparison of partial excision with simple section of the transverse carpal ligament in the treatment of carpal tunnel syndrome

In the surgical treatment of carpal tunnel syndrome, debate has commonly focused on whether decompression should be performed by open or blind techniques. Contrarily, the goal of the present study was to determine whether instead of simple section, partial excision of the transverse carpal ligament has contributed to better results. Because complete healing of the transverse carpal ligament observed during reoperations has been reported elsewhere, the charts of 75 carpal tunnel syndrome patients who had been treated with open technique at Dokuz Eylül University were reviewed. Statistical analysis was performed using the Fisher's exact test and Student's t test when appropriate. Thirty-five patients had been treated with simple section of the transverse carpal ligament, whereas 40 had been treated with partial excision. Internal neurolysis was also performed in 19 of the patients, 11 of whom were treated with partial excision. The average follow-up time was 3.8 years. The comparisons regarding the overall operative outcomes did not show any significant difference between the two different techniques of releasing the transverse carpal ligament. In patients treated without neurolysis, results of partial excision of the transverse carpal ligament improved when compared with those of simple section, but this superiority was not statistically significant. There seemed to be statistically higher reoperation rates and worse outcomes after neurolysis (p < 0.05). Reoperation was required in eight patients (11 percent). Five of the patients who underwent reoperation had initially been treated with partial excision and neurolysis, whereas two had been treated with simple section and neurolysis. Another patient who had undergone reoperation had initially undergone only simple section. The mean time to return to work or daily activities did not differ between the types of applied technique for releasing the transverse carpal ligament. However, neurolysis lengthened these periods significantly when performed (p < 0.05). In the present study, partial excision of the transverse carpal ligament without adding neurolysis offered relatively better results than simple section. Verification of this finding endoscopically, if applicable, may improve the success rate of surgical therapy in patients with carpal tunnel syndrome.     

Evaluation of the carpal tunnel based on 3-D reconstruction from MRI

While deviated wrist postures have been linked to the development of carpal tunnel syndrome, the relative contributions of posture-related changes in size, shape and volume of the carpal tunnel contribute to median nerve compression are unclear. The purpose of this study was two-fold: (1) to reconstruct the carpal tunnel from MRI data in neutral and non-neutral (30 degrees extension, 30 degrees flexion) wrist postures, and (2) to evaluate errors associated with off-axis imaging. Three-dimensional reconstruction of the carpal tunnels of 8 volunteers from the university community revealed that the orientation of the carpal tunnel was not directly explained by external wrist angle. The average orientation of the carpal tunnel was extended in all postures, ranging from 25 degrees +/-9 degrees in extension, 13 degrees +/-5 degrees in neutral and 4 degrees +/-4 degrees in the flexed wrist. Changing the orientation of the imaging plane to be perpendicular to the reconstructed carpal tunnel revealed that axial images overestimated cross-sectional area by an average of nearly 10% in extension, 4% in neutral and less than 1% in flexion. Similarly, adjusting the imaging plane to be perpendicular to external wrist angle overestimated cross-sectional area by an average of 2% in extension, 4% in neutral and 24% in flexion. Distortion of the carpal tunnel shape also became evident with rotation of the imaging plane. The data suggest that correction for the orientation of the carpal tunnel itself to be more appropriate than relying on external wrist angle. Computerized reconstruction provided detailed anatomic visualization of the carpal tunnel, and has created the framework to develop a biomechanical model of the carpal tunnel. Similar reconstruction of the tissue structures passing through (median nerve and flexor tendons) and entering the carpal tunnel (muscle tissue) will enable evaluation and partitioning of median nerve injury mechanisms.     

Adaptation of the Transverse Carpal Ligament Associated with Repetitive Hand Use in Pianists

The transverse carpal ligament (TCL) plays a critical role in carpal tunnel biomechanics through interactions with its surrounding tissues. The purpose of this study was to investigate the in vivo adaptations of the TCL’s mechanical properties in response to repetitive hand use in pianists using acoustic radiation force impulse (ARFI) imaging. It was hypothesized that pianists, in comparison to non-pianists, would have a stiffer TCL as indicated by an increased acoustic shear wave velocity (SWV). ARFI imagining was performed for 10 female pianists and 10 female non-pianists. The median SWV values of the TCL were determined for the entire TCL, as well as for its radial and ulnar portions, rTCL and uTCL, respectively. The TCL SWV was significantly increased in pianists relative to non-pianists (p < 0.05). Additionally, the increased SWV was location dependent for both pianist and non-pianist groups (p < 0.05), with the rTCL having a significantly greater SWV than the uTCL. Between groups, the rTCL SWV of pianists was 22.2% greater than that of the non-pianists (p < 0.001). This localized increase of TCL SWV, i.e. stiffening, may be primarily attributable to focal biomechanical interactions that occur at the radial TCL aspect where the thenar muscles are anchored. Progressive stiffening of the TCL may become constraining to the carpal tunnel, leading to median nerve compression in the tunnel. TCL maladaptation helps explain why populations who repeatedly use their hands are at an increased risk of developing musculoskeletal pathologies, e.g. carpal tunnel syndrome.     

A meta-analysis of randomized controlled trials comparing endoscopic and open carpal tunnel decompression

Controversy exists regarding the benefit of endoscopic carpal tunnel release versus open carpal tunnel release in terms of grip/pinch strength, scar tenderness, pain, return to work, reversible/irreversible nerve damage, and adverse effects. Although a number of randomized controlled trials and systematic reviews have been published on the subject, to date, no large definitive randomized controlled trial or meta-analysis has been performed comparing endoscopic to open carpal tunnel release. This meta-analysis was undertaken to address the effectiveness of endoscopic carpal tunnel release relative to open carpal tunnel release. Key outcome measures from 13 randomized controlled trials were extracted and statistically combined. Heterogeneity was observed in three of the outcomes (i.e., grip strength, pain, and return to work), but the causes of heterogeneity could not be explained because of insufficient detail in the reported studies. Using the Jadad et al. scale, nine of 13 studies were of low methodologic quality. The effect sizes were compared between the studies that were rated as high quality and the studies that were rated as low quality on the Jadad et al. scale. Similarly, the studies that were rated as high quality on the Gerritsen et al. scale were compared with those that were rated as low quality. No clinically significant difference in effect sizes was apparent between studies of high and low methodologic quality. This meta-analysis supports the conclusion that endoscopic carpal tunnel release is favored over the open carpal tunnel release in terms of a reduction in scar tenderness and increase in grip and pinch strength at a 12-week follow-up. With regard to symptom relief and return to work, the data are inconclusive. Irreversible nerve damage is uncommon in either technique; however, there is an increased susceptibility to reversible nerve injury that is three times as likely to occur with endoscopic carpal tunnel release than with open carpal tunnel release.     

A systematic review of reviews comparing the effectiveness of endoscopic and open carpal tunnel decompression

Controversy persists regarding the benefit of endoscopic carpal tunnel release compared with open carpal tunnel release for pain, numbness, strength, return to work and function, scar tenderness, and complications. For surgeons, a recommended first source of information on treatment effectiveness is a review of high-methodologic-quality articles. This review of reviews was undertaken to answer this clinical question regarding these outcomes. Cochrane, MEDLINE, EMBASE, CINAHL, and HealthSTAR databases were searched using the key words "endoscopic carpal tunnel," with limits "review or overview" and dates from 1989 to present. Five key journals were hand-searched. Any review with a reference to at least one randomized controlled trial that compared endoscopic carpal tunnel release to open carpal tunnel release was to be included. Two reviewers independently scanned titles and abstracts for potential relevance. Selection as relevant was confirmed through a review of full texts. Disagreements were resolved through discussion and consensus. The selected reviews were assessed for methodologic quality on the basis of the scale of Hoving et al. Of 48 articles initially identified, seven pertinent reviews were selected. Of these seven, three reviews of high methodologic quality concurred that there is no difference between the two techniques in symptom relief and that the evidence is conflicting for return to work and function. The risk of permanent median nerve injury does not differ between the techniques. The reviews indicated that the endoscopic carpal tunnel release technique is worse in terms of reversible nerve injury but superior in terms of grip strength and scar tenderness, at least in short-term follow-up. Several trials have not been incorporated in these reviews and statistical pooling has not been conducted. Further systematic review with meta-analysis may permit more definitive conclusions about the relative effectiveness of these two techniques, particularly with regard to return to work and function.     

Estrogen and progesterone receptors in carpal tunnel syndrome

Carpal tunnel syndrome (CTS) is a compression median nerve neuropathy common in women at menopausal age. The aim of this work was to study immunohistochemically the expression of estrogen (ER) and progesterone (PR) receptors in CTS and control specimens. Biopsies of transverse carpal ligament (TCL) and flexor tendon synovitis were collected from 23 women and from 7 men undergoing surgery for median nerve decompression at the wrist for CTS. In TCL and synovial tissue, cells expressed ER and PR with statistically significant differences related to the age and sex of patients. Immunoreactivity was observed in fibroblasts of TCL, and in lining cells and fibroblasts of synovial tissue. In women, the number of ER-positive cells in the TCL and synovial tissue increased with the age, peaking at 55-70 years, and then decreasing. PR-immunoreactivity was observed only in fibroblasts of TCL and its expression decreased with age, while no immunolabeling was found in the synovial tissue. In TCL samples, the number of ER- and PR-positive cells in non-CTS patients was significantly lower than in CTS patients. These results demonstrate that ER and PR are present in TCL and flexor tendon synovitis, suggesting a role for sex steroid hormones in the pathogenesis of CTS disease.     

Comparison of the Effects of Flexion and Extension of the Thumb and Fingers on the Position and Cross-Sectional Area of the Median Nerve

Objective

To assess the separate effects of thumb and finger extension/flexion on median nerve position and cross-sectional area.

Methods

Ultrasonography was used to assess median nerve transverse position and cross-sectional area within the carpal tunnel at rest and its movement during volitional flexion of the individual digits of the hand. Both wrists of 165 normal subjects (11 men, 4 women, mean age, 28.6, range, 22 to 38) were studied.

Results

Thumb flexion resulted in transverse movement of the median nerve in radial direction (1.2±0.6 mm), whereas flexion of the fingers produced transverse movement in ulnar direction, which was most pronounced during flexion of the index and middle fingers (3.2±0.9 and 3.1±1.0 mm, respectively). Lesser but still statistically significant movements were noted with flexion of the ring finger (2.0±0.8 mm) and little finger (1.2±0.5 mm). Flexion of the thumb or individual fingers did not change median nerve cross-sectional area (8.5±1.1 mm²).

Conclusions

Volitional flexion of the thumb and individual fingers, particularly the index and middle fingers, produced significant transverse movement of the median nerve within the carpal tunnel but did not alter the cross-sectional area of the nerve. The importance of these findings on the understanding of the pathogenesis of the carpal tunnel syndrome and its treatment remains to be investigated.     

A fluid-immersed multi-body contact finite element formulation for median nerve stress in the carpal tunnel

Carpal tunnel syndrome (CTS) is among the most important of the family of musculoskeletal disorders caused by chronic peripheral nerve compression. Despite the large body of research in many disciplinary areas aimed at reducing CTS incidence and/or severity, means for objective characterization of the biomechanical insult directly responsible for the disorder have received little attention. In this research, anatomical image-based human carpal tunnel finite element (FE) models were constructed to enable study of median nerve mechanical insult. The formulation included large-deformation multi-body contact between the nerve, the nine digital flexor tendons, and the carpal tunnel boundary. These contact engagements were addressed simultaneously with nerve and tendon fluid-structural interaction (FSI) with the synovial fluid within the carpal tunnel. The effects of pertinent physical parameters on median nerve stress were explored. The results suggest that median nerve stresses due to direct structural contact are typically far higher than those from fluid pressure.     

Arteriovenous malformation of a persistent median artery with a bifurcated median nerve

A patient with arteriovenous malformations of the volar forearm and hand arising from a persistent median artery with an associated bifid median nerve is presented. Surgeons should be aware of high median nerve bifurcations, particularly when a persistent median artery is identified, and should remember that additional structures that can lead to nerve compression may be present in the carpal tunnel. Specifically, more than one median nerve may need to be identified and protected in such cases.     

Apparent transverse compressive material properties of the digital flexor tendons and the median nerve in the carpal tunnel

Carpal tunnel syndrome is a frequently encountered peripheral nerve disorder caused by mechanical insult to the median nerve, which may in part be a result of impingement by the adjacent digital flexor tendons. Realistic finite element (FE) analysis to determine contact stresses between the flexor tendons and median nerve depends upon the use of physiologically accurate material properties. To assess the transverse compressive properties of the digital flexor tendons and median nerve, these tissues from ten cadaveric forearm specimens were compressed transversely while under axial load. The experimental compression data were used in conjunction with an FE-based optimization routine to determine apparent hyperelastic coefficients (μ and α) for a first-order Ogden material property definition. The mean coefficient pairs were μ=35.3 kPa, α=8.5 for the superficial tendons, μ=39.4 kPa, α=9.2 for the deep tendons, μ=24.9 kPa, α=10.9 for the flexor pollicis longus (FPL) tendon, and μ=12.9 kPa, α=6.5 for the median nerve. These mean Ogden coefficients indicate that the FPL tendon was more compliant at low strains than either the deep or superficial flexor tendons, and that there was no significant difference between superficial and deep flexor tendon compressive behavior. The median nerve was significantly more compliant than any of the flexor tendons. The material properties determined in this study can be used to better understand the functional mechanics of the carpal tunnel soft tissues and possible mechanisms of median nerve compressive insult, which may lead to the onset of carpal tunnel syndrome.